3-PROBE VOLTAMMETRIC CHARACTERIZATION OF OCTADECANETHIOL SELF-ASSEMBLED MONOLAYER INTEGRITY ON GOLD ELECTRODES

The passivating behaviour of self-assembled octadecanethiol monolayers on polycrystalline gold electrodes was tested by means of the cyclic voltammetry technique in the presence of three different redox probe m olecules. The three compounds chosen for this purpose, ruthenium hexam ine chloride [Ru(NH3)Cl-3], potassium ferrocyanide [K4Fe(CN)(6)] and b enzoquinone, were selected on the basis of the differences in their he terogeneous electron transfer rate constants and their hydrophobic/hyd rophilic character. Our studies show that passivating properties of oc tadecanethiol monolayers against these probes are different. The resul ts obtained are discussed in terms of Tafel approach and monolayer int egrity. It appears that the screening of self-assembled films with dif ferent probes is necessary in order to properly characterise the film integrity and passivating behaviour. Additionally, the interaction of octadecanethiol molecules with a polycrystalline gold surface was eval uated by means of potentiostatic pulse measurements.